1. Field of the Invention
The present invention generally relates to subscriber-system transmission apparatuses, and particularly relates to a subscriber-system transmission apparatus which is equipped with interface connectable to any types of switches of the IDLC type or the UDLC type and connectable to various switches of different vendors.
2. Description of the Related Art
FIG. 15 is an illustrative drawing showing a remote-station switch system having a UDLC (universal digital loop carrier) network configuration. FIG. 16 is an illustrative drawing showing a remote-station switch system having an IDLC (integrated digital loop carrier) network configuration.
The remote-station switch system of FIG. 15 having a UDLC network configuration is of a type that is used together with an analog switch. A subscriber-system transmission apparatus 1 shown in FIG. 15, which serves as a remote terminal RT, covers subscriber terminals that are scattered around in remote areas (CSA: carrier service areas) far away from an analog switch 4. The subscriber-system transmission apparatus 1 connects these subscriber terminals to the analog switch 4 via optical-fiber transmission lines. In one example of the UDLC network configuration, the subscriber-system transmission apparatus 1 is connected to the analog switch 4 via an optical-fiber transmission line, an optical transmission apparatus 9 having optical-signal multiplexing/demultiplexing functions, and a transmission apparatus 8 having electrical-signal multiplexing/demultiplexing functions. In another example of the UDLC network configuration, the subscriber-system transmission apparatus 1 is connected to the analog switch 4 via an optical-fiber transmission line and a center-station-system (COT) transmission apparatus 5 having optical-signal multiplexing/demultiplexing functions.
The remote-station switch system of FIG. 16 having an IDLC network configuration is of a type that is used together with a digital switch. In one example of this configuration, the subscriber-system transmission apparatus 1 is connected to a digital switch 3 of a TR08 type via an optical-fiber transmission line and the optical transmission apparatus 9 having optical-signal multiplexing/demultiplexing functions. In another example of this configuration, the subscriber-system transmission apparatus 1 is connected to a digital switch of a TR303 type via an optical-fiber transmission line and the optical transmission apparatus 9. The former example corresponds to a scheme in which signaling is incorporated into subscriber lines when it is transmitted, and the latter example corresponds to a scheme in which signaling is transmitted via another path. In either example of the IDLC network configuration, the transmission apparatus 8 having electrical-signal multiplexing/demultiplexing functions is made obsolete while it is of necessity in the UDLC network configuration.
The subscriber-system transmission apparatus 1 that is connected to the analog switch 4 or the digital switch 2 or 3 covers ISDN subscriber terminals. In what follows, a description will be given of an ISDN multiplexing scheme.